Manuela Carmena Castrillo (Spanish pronunciation: [maˈnwela kaɾˈmena kasˈtɾiʎo]; born 9 February 1944) is a retired Spanish lawyer and judge who served as Mayor of Madrid from June 2015 to June 2019. She was a member of the General Council of the Judiciary.

She was born on 9 February 1944 in Madrid, in the area near the Dehesa de la Villa. Both sides of her family had a background in small business: her father Carmelo (a native of Toledo) ran a shirt shop at the corner of Gran Vía and Chinchilla Street in central Madrid. Her mother, meanwhile, worked as a cashier. She attended the French School of the Black Ladies. During her time as a student, Carmena served as voluntary worker in a preserves factory run by the Servicio Universitario del Trabajo.

After graduating in law in 1965 from the University of Valencia, she became a legal representative of workers and detainees during the Francoist State and was co-founder of the labour law office where the 1977 Atocha massacre took place.

Carmena, who joined the Communist Party of Spain (PCE) in 1965, married architect Eduardo Leira in 1967; they have had two children: Eva and Manuel. She ran as a candidate in the PCE list for the 1977 general election in the constituency of Madrid. She had left the party by 1981.

After passing public examinations to become a judge, she started her judicial career in January 1981. As a judge she began an almost solitary fight to prevent corruption in existing courts. In 1986 she received the National Human Rights Award. She was a founding member of the progressive association Judges for Democracy. Judge of Penitentiary Vigilance and head of the Penitentiary Vigilance Court No. 1 of Madrid, she was elected senior judge of Madrid in 1993. She was appointed as member of the General Council of the Judiciary (proposed by United Left) and served from 1996 to 2001.

After retiring from the judiciary in 2010, Carmena moved on to become a member of the Patronato de la Fundación Alternativas, a think tank with ties to the Spanish Socialist Workers' Party (PSOE), and whose members included the former Socialist prime ministers Felipe González and José Luis Rodríguez Zapatero. Carmena was Chair-Rapporteur of the United Nations Working Group on Arbitrary Detention, and as such, she has visited Equatorial Guinea, Honduras, Nicaragua and South Africa, among other countries. In September 2011, Carmena was appointed advisor to the Patxi López cabinet of the Basque Government in the area of assistance to victims of police abuse.

Carmena Castrillo founded the supportive cooperative "Yayos emprendedores" (literally, "entrepreneur grannies"), which manages a small retail business selling children's games, clothing and shoes made by prisoners at the Alcalá de Guadaira jail in Seville.

Carmena headed Ahora Madrid's ticket in the Madrid local election held on 24 May 2015. After Ahora Madrid made a coalition deal with the PSOE, Carmena was elected as Mayor on 13 June 2015, obtaining the votes of 29 out of 57 councillors and thereby winning a narrow majority.